The invention relates to a closure element for closing an end of a pipe, in particular a steel pipe.
Closure elements of this type are used typically to protect pipe ends when pipes are transported and the interior of the pipe is to be protected against the ingress of dirt or moisture. Also, if the pipes are welded or bolted on the building site, the pipe ends must be protected against damage during transportation.
Attachable closure elements have hitherto been established as temporary protection for pipe ends. Closure elements of this type consist of a base cover and of a cylindrical outer casing consisting of an elastic synthetic material and formed as a collar, wherein the collar engages around the outer periphery of the pipe end and becomes more or less fixedly clamped to the pipe in a non-positive manner by means of elastic resilience.
However, these closure elements are faced with the problem that, on account of the collar which lies on the outer surface, the closure elements frequently become detached from the pipe end or become damaged during transportation e.g. as a result of shaking movements or relative movements of the pipes with respect to each other, and therefore the protective function is no longer provided. Moreover, it is necessary to adhere to very narrow tolerances for the inner diameter of the collar, so that on the one hand the collar lies in a non-positive manner against the pipe surface and on the other hand can be attached without excessive application of force.
Documents DE 10 2006 045 592 A1 and DE 84 14 522 disclose closure elements which are not attached to the pipe end in the manner described above but rather become fixedly clamped inside the pipe. For this purpose, the cover of these closure elements has elastic clamping elements which are distributed over the periphery on the side facing towards the interior of the pipe and, when inserted into the pipe, become clamped with the inner surface of the pipe by means of elastic resilience.
In the case of closure elements of this type, the risk of the closure elements becoming detached from the pipe end is less than in the case of the previously described closure elements, as the base cover lies flush against the end surface of the pipe end and does not engage around the pipe end.
However, in the case of these closure elements, gripping lugs for removing the closure element protrude beyond the outer periphery of the pipe, so that in this case contact points are also present which can lead to the closure element becoming inadvertently detached from the pipe.
Moreover, in the case of both solutions it is disadvantageous that e.g. in the case of a constant outer diameter and greatly varying inner diameters, a large number of different closure elements is required, since the elastic clamping elements of these known closure elements can only compensate for small fluctuations in the inner diameter which in the range of rolling tolerances are up to several mm.
In the case of pipes whose wall thicknesses can vary, depending upon the order, by up to 10 cm or more while the outer diameter remains constant at e.g. 600 mm, as is possible e.g. in the case of seamless, hot-rolled pipes produced by means of the pilger method, the known closure elements which are configured for clamping within the framework of rolling tolerances only to a nominal inner diameter can no longer be used.
In such cases, closure elements designed in accordance with the respective wall thicknesses must be used. The provision of the requisite large number of closure element variants is very complicated logistically, is cost-intensive and thus uneconomical.
Moreover, laid-open document US 2008/0236691 A1 already discloses plugs used to close a plurality of bores in a concrete pipe. The total of four bores in the casing surface of the concrete pipe are used for attaching a cable in order to handle the concrete pipe for laying in the ground. If the bores are no longer required they can be closed by the plugs. Each of the plugs consists of a disk, a support part and elastic fins. The planar disk has a diameter which is larger than the diameter of the bores in order to cover them. The underside of the disk facing the bore is adjoined centrally by the cruciform support part which extends away from the underside and thus protrudes into the bore in the assembled condition. The support part has an outer diameter which is somewhat smaller than the inner diameter of the bore. In order to be able to attach the plug in the bore, the four ends of the cruciform support part are externally adjoined in each case by elastic fins whose outer ends have a diameter which is larger than the inner diameter of the bore. Upon insertion of the support part with the fins into the bore, the fins yield in an elastic manner and lie with their outer ends internally against the inner wall of the bore. The elastic resilience of the fins serves to hold the plug in the bore. The plug with the disk, the support part and the fins is produced as a one-piece synthetic material injection-moulded part.